1. Field of the Invention
This invention relates to improvements in rotating drive mechanisms or devices, and more particularly to improvements in rotating harmonic drive mechanisms.
2. Relevant Background
Harmonic drives traditionally use an internal spur gear with an external gear that orbits eccentrically within it. Such drives generally provide high gear reduction ratios in a compact package. Such drives generally use meshing gear teeth. The axes of these gears do not coincide, but are slightly offset, and one axis orbits the other at a uniform radial distance. Such harmonic drives are positionable to desired locations, but typically use frictional inefficiencies between the gears to cause a "binding" to lock the mechanism at the finally adjusted position. Often, such devices may require special additional locking mechanisms to maintain the drive in its adjusted position.
Although harmonic drives have many applications, one example in which such drives are particularly useful is in adjustable seats of the type used in aircraft, or other vehicles. Typically such seats have a seat back that may be positionably, selectively rotated forward or backward from a rear portion of the bottom seat cushion, so that the user can adjust his degree of reclination. Also, often such seats have a headrest or head support that may be adjustably rotatable to conform to the users preference or body posture. Some seats also have lower back supporting portions that may be moved into or away from the back of the seat to conform to the small of the user's back. Such seat backs, head rests, and lower back supporting structures may be positioned by means of a rotatable or harmonic drive of the type described herein.